Pressure fluctuation in gas-solid agitated fluidized bed

doi:10.11949/j.issn.0438-1157.20151253

Abstract

Abstract:

Gas-solid agitated fluidized beds can be used to improve the fluidization performance of sticky polymer particles. Experimental pressure fluctuation signals were analyzed with statistics analysis, power spectrum analysis and wavelet analysis for investigating the influence of agitation speeds and types of agitators on the fluidization characteristic. Due to the effects of suppression and breakage on bubbles caused by agitation, lower pressure fluctuation amplitude and smaller bubbles were found in the agitated fluidized bed compared to general fluidized bed. The synergy between gas flow and agitation occurred in the agitated fluidized bed. For a gas-solid fluidized bed with an anchor impeller or a frame impeller, sufficiently high agitation speed was needed to improve fluidization performance. However, for self-cleaning agitator, higher agitation speed engendered adverse phenomena of gas short circuit and particles accumulation near the blades. Therefore, the feasible agitation speed was recommended for extending the application of the new self-cleaning agitator in industry.

Key words: fluidized bed, agitation, pressure fluctuation, statistics analysis, multiphase flow, coalescence

摘要：

气固搅拌流化床反应器可用于黏结性聚合物颗粒的流态化过程,流化床中通气湍动与搅拌的相互作用关系仍不明确。通过压力脉动的统计分析、功率谱分析和小波分析,考察了搅拌桨型式和搅拌转速对流态化特性的影响规律。实验发现,搅拌转速和搅拌桨型式对床层压力影响较小,但对压力脉动影响显著。搅拌流化床中搅拌与通气湍动对流态化共同作用,双层锚式桨、框式桨等小桨叶面积的搅拌桨在较高转速条件下能强化流态化过程,与普通流化床相比具有更小的气泡尺寸和压力脉动,搅拌可抑制气泡聚并、破碎气泡,维持床层均匀流态化;而新型具有大桨叶面积的自清洁桨的搅拌作用强烈,在较高的转速下易形成桨叶前方的颗粒堆积和桨叶后方的气体短路等非正常流化现象,适宜于中等转速的操作条件。

关键词: 流化床, 搅拌, 压力脉动, 统计分析, 多相流, 聚结

CLC Number:

TQ021

ZHANG Yongjun, WANG Jiajun, GU Xueping, FENG Lianfang. Pressure fluctuation in gas-solid agitated fluidized bed[J]. CIESC Journal, 2016, 67(2): 494-503.

张永俊, 王嘉骏, 顾雪萍, 冯连芳. 气固搅拌流化床中压力脉动特性[J]. 化工学报, 2016, 67(2): 494-503.

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